In vitro, ICOS/ICOSL blockade significantly reduced the generation of MM cell‐induced inhibitory CD4+ Treg cells,55, 56 and lenalidomide, a clinically approved anti‐MM immunomodulatory drug, could inhibit ICOSL expression in MM cells57 and enhance PD‐1/PD‐L1 blockade‐induced anticancer immunity in MM patients.58 Here, ICOSLG is linked to Miyoshi myopathy.